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I've been shopping anemometers and the price difference makes the FP almost "too good to be true" which makes me question it's quality and accuracy. I was burned a looooong time ago by a FP meter and I'm VERY hesitant to buy another.

OK,
Here is a comparison of the accuracy of the Fieldpiece STA 2 compared to my furnace ECM.

I would love to see how that traverse compares to one 30" or so closer to the furnace, which to me would be pretty close to the "ideal" spot. Also compared to the one in your earlier video, and the test holes in your drop around the air cleaner. Maybe one right before the big drop to the air cleaner. Maybe one right at the top of the drop. Just a few less than ideal spots.

I appreciate you taking the time to make and post the above videos. Id be happy just to see the numbers without a video on the other spots. I aint trying to over-work you, just curious.

I would love to see how that traverse compares to one 30" or so closer to the furnace, which to me would be pretty close to the "ideal" spot. Also compared to the one in your earlier video, and the test holes in your drop around the air cleaner. Maybe one right before the big drop to the air cleaner. Maybe one right at the top of the drop. Just a few less than ideal spots.

I appreciate you taking the time to make and post the above videos. Id be happy just to see the numbers without a video on the other spots. I aint trying to over-work you, just curious.

Closer to the furnace should yield exactly the same results, I wanted to have a straight run before and after to get the most laminar flow, you are correct however that the downstream location is ideal also. The initial spot I traversed was about 10% higher due to the turbulence from the turn. The velocity was very high at the back of the duct. I also tested a spot right after the EAC, it was almost exactly the same as the spot I did in the second video.

I did notice that the probe position is less sensitive than a Pitot tube, and a little more sensitive than a small vane, but if you are careful with the probe position it is easy to repeat the result +/- 10-12 CFM every time.

Great video. Always love the tips and tricks Jim. Just one thing that I saw though is the magnet is either too weak or the plastic is too slippery to hold the units weigh. It started slipping just as you set it without the weight of the wand. It might be hard to work the unit hands free anyway but just an observation
JP You have a 510 don't you? have you considered using a pilot tube for air flow?

Jim, did you get your airflow corrected ? What was it , dip switches incorrect ?

Timber,

dip switch settings, I had messed with it earlier and set it for 4tons of cooling instead of 3 tons. In addition I have the airflow set to 110% for the additional capacity and efficiency on second stage hence the 1740 CFM reading. I play with my system once in awhile and must have either set it wrong, or forgot to set it back.

A vane will tend to read a higher airflow than a hot-wire or a Pitot if the location is in favor of the hot-wire or Pitot tube, non turbulent air. This is because a vane measures airflow independent of air density. As air density decreases, (relative humidity goes up, temperature goes up, or barometric pressure goes down) the hot-wire assumes that there is less air going over it. Temperature, relative and barometric pressure all affect the air density. The Fieldpiece STA2 compensates for only air temperature which is the largest contributor to density changes. But if the RH is high or the barometric pressure low (typically do to elevation) the hot wire or vane will indicate a lower airflow then actually exists. To get everything apples to apples, you really have to convert everything to pounds mass flow, and make corrections for density.

Although a mini vane is my first choice for airflow simply because of the work that I do and the desire for very precise airflow measurement, it is cost prohibitive for a lot of technicians. With the basic density correction in the Fieldpiece STA2 and a relatively low cost it is a perfect airflow instrument for the work that 95% of the technicians will encounter. Aside from initial cost, the STA2 has the advantage of a smaller head which means smaller holes in the duct work, automatic calculation of areas, and a fairly intuitive operation. Where additional correction might be required is above 3000-4000', and at humidity levels over 80%. If air density is not corrected, when densities are far outside of the calibration parameters in regard to RH or barometric pressure, a reading that is low by up to 10% could very easily happen. Provided the point of measure is carefully selected and hot-wire is used correctly, it will provide a very accurate airflow measurement. Taking that into account, I have no objections to recommending the Fieldpiece STA2 for airflow measurement.